Chem Exam 3 Review

What does the octet rule state for first-row atoms in bonding?

All atoms bond in order to achieve eight electrons in their valence shell.

Who developed the Lewis Structure?

Gilbert N. Lewis.

What is a polar covalent bond?

A bond where the sharing of electrons is uneven, leading to slight positive and negative poles.

What does VSEPR theory explain about molecular shapes?

Molecules are shaped due to repulsions between electrons and attractions to the central atom.

How is the steric number (SN) calculated?

By adding the number of lone pairs and bonding pairs together.

What is the formula for Boyle’s Law?

P1V1 = P2V2.

Describe Graham's Law of Effusion.

It states that gas will escape through a semi-permeable membrane at a rate dependent on the speed of its molecules.

What does the ideal gas law formula (PV = nRT) represent?

It combines Boyle's, Charles's, and Avogadro's laws to relate pressure, volume, number of moles, and temperature of a gas.

What is internal energy change represented by?

ΔE = E_final - E_initial.

What is the significance of the first law of thermodynamics?

It states that the total energy change of a closed system and its surroundings is equal in magnitude but opposite in sign.

What does enthalpy (H) measure in a thermodynamic system?

It measures the total internal energy plus the pressure-volume work done.

How does heat capacity relate to temperature change?

Molar heat capacity (cp) is the energy required to raise the temperature of 1 mole of a substance by 1 degree Celsius.

Define the concept of resonance in chemistry.

It refers to the various valid Lewis structures that can be drawn for a molecule, depicting the delocalization of electrons.

What is a formal charge?

A theoretical charge calculated to determine the charge distribution in a molecule, ideally aiming for zero.

How does the concept of free radicals relate to the octet rule?

Free radicals contain an odd number of electrons and therefore do not complete the eight-electron requirement.

What does the kinetic molecular theory state about gas particles?

Gas molecules have tiny volumes compared to the total volume they occupy and move randomly and constantly.

What is atmospheric pressure?

The pressure exerted by the weight of the atmosphere, measured in various units such as mmHg and atm.

What is the difference between exothermic and endothermic reactions?

Exothermic reactions release energy to the surroundings, while endothermic reactions absorb energy from the surroundings.

What role do lone pairs play in Lewis Structures?

Lone pairs are pairs of electrons that are not involved in bonding and are critical for determining molecular geometry.

What is the relationship between pressure and temperature in Amonton's Law?

Pressure and temperature are directly proportional to each other when volume remains constant.

Explain the relationship between electrons and electronegativity in polar bonds.

Electronegativity is a measure of an atom's ability to attract and hold onto electrons within a bond.